In an electrical discharge machine, a workpiece is arranged while a wire electrode is moved from an upper support part to a lower support part, and the workpiece is chipped away by electrical discharge generated between the wire electrode and the workpiece (Patent Document 1 and Patent Document 2). The workpiece is formed with a cutting surface according to the wire electrode. The upper support part and the lower support part are configured of dies (cylinder provided with an insertion hole through which the wire electrode is passed) formed of a mineral (diamond, ruby, or the like) that is excellent in wear resistance with respect to the wire electrode or configured of an upper guide roller and a lower guide roller. The upper support part and the lower support part are arranged such that the dies or the upper guide roller and the lower guide roller are aligned on the same vertical line. Since the wire electrode moves downward from above, the cutting surface of the workpiece is also a vertical surface. When the wire electrode that moves from the upper support part toward the lower support part is angled, the cutting surface is also angled.
In an electrical discharge machine disclosed in Patent Document 1, an upper support arm 5 that supports an upper support part (guide head 3) and a lower support arm 5 that supports a lower support part (guide head 4) each have a gimbal suspension, and the upper support part is displaced back and forth and side to side with respect to the lower support part such that a wire electrode is angled. When the upper support part is merely displaced in this arrangement, there is a risk of the wire electrode being rubbed excessively against a die (support member 22) forming the upper support part and the lower support part. To prevent this, in the electrical discharge machine disclosed in Patent Document 1, a guide roller (pulley 21, i.e., guiding means) around which the wire electrode is wound is arranged immediately above the upper support part and immediately below the lower support part, such that the upper support part and the lower support part are angled in accordance with the angle of the wire electrode and the moving wire electrode enters or exits along an insertion hole of the die (claim 1 and FIGS. 1 to 3 in Patent Document 1).
In an electrical discharge machine disclosed in Patent Document 2, a wire electrode (wire 8) is wound around guide rollers (shaft 38 and shaft 37) provided to an upper support part (upper machining head 14) and a lower support part (lower machining head 13), respectively, that are displaced in advance. The upper support part is provided to an auxiliary table 20 that is movable in two orthogonal directions in a horizontal plane, and is rotatable so as to change the direction of the guide roller with the wire electrode (wire 8) as the center. The lower support part is provided to a support arm (arm 11) that is relatively fixed in position, and is rotatable so as to change the direction of the guide roller with the wire electrode (wire 8) as the center. As a result, the upper support part moves in the two orthogonal directions in the horizontal plane in accordance with the auxiliary table to change the angle of the wire electrode, and the upper support part and the lower support part are rotated to change the direction of the guide roller such that a vertical plane in which the angled wire electrode lies and the rotation plane of the guide rollers of the upper support part and the lower support part coincide (the lower left column on page 4 to the upper left column on page 5 in Patent Document 1).
Patent Document 1: Japanese Examined Patent Publication No. S63-036888
Patent Document 1: Japanese Patent Application Publication No. S63-260724